A miniature electronic device (e.g., a portable function calculator) usually inputs a mathematical expression by using a keyboard and displays the inputted mathematical expression on a liquid crystal display. A prior art miniature electronic device indicates a name of a variable in a mathematical expression and separately indicates a value (or values) of the variable on a display screen when a mathematical expression, e.g., &lt;sin A+cos B+CD/8+E&gt; including variables A, B, C, D and E is inputted, the expression is indicated on the first line and values for the variables A, B, C, D and E are indicated on the second and lower lines on a display screen. The result of calculation on the mathematical expression is stored in a variable Ans and its value is indicated on the lowest line. Thus, the conventional miniature electronic device (e.g., a portable function calculator) indicates not values but variable-names in a mathematical expression on a display screen when inputting variables.
However, the prior art miniature electronic device has such a limited display capacity that it can display only an input mathematical expression with a result of calculation in a usual calculation mode. To indicate a table of variable-values, it is necessary to change over a screen image to a specified mode. In other words, the prior art electronic device can not display all necessary information at a time on its display screen since the display screen is short in the number of lines and the number of digits per line. Namely, only a part of information can be displayed on the display screen due to the insufficient capacity of its display.
Accordingly, variables A, B, C, D and E and its values must be displayed by changing the screen image by scrolling. The mathematical expression must be also displayed in a specified portion on the screen by scrolling. Thus, the display of the variables and mathematical expressions require the troublesome scrolling operations.
One of prior arts relating to the present invention is a technique of substituting a variable-name by a variable-value. Japanese Laid-open Patent Publication (TOKKAI HEI) No. 6-119158 discloses a variable replacing device, which is explained as follows:
A variable replacing device is composed mainly of a converting section for reading a text to be converted, reading a variable-value from a variable-value control portion and replacing a variable-name contained in the text with the variable-value and a variable-result outputting portion for outputting the result onto a output device (e.g., a display or printer) or a conversion requesting source program.
In the converting portion, a variable-name extracting portion extracts a name of a variable by retrieving it in a text to be converted, a variable-value getting portion reads a value of the variable corresponding to the variable-name from the variable-value control portion, a variable-name analyzing portion analyzes the variable-name, a variable-value converting portion changes the form of representing the variable-value according to the analyzing result and variable-value replacing portion substitutes the variable-name by the variable-value. A variable-value setting portion is operated from a terminal to set and change a variable-name and a variable-value in the variable-value control portion. Thus, the variable-name in the text to be converted is substituted by the variable-value.
However, the processing unit is intended to change a variable-name in an already prepared text to be converted by a variable-value. Therefore it differs from the present invention by its object of conversion. This prior art device can not perform changing-over the indication from a variable-name to a variable-value and vice verse at any time if the need be and can not replace a variable-name with a variable-value while inputting a text to be converted.
As described above, the prior art electronic device can not easily refer to a variable-value since a variable-value and a mathematical expression must be referred separately by scrolling.